1. Field of the Invention
The present invention is directed to a method for forming molecular layers having high density of primary amine groups on solid supports.
More particularly, this invention relates to a method for forming either linear or hyper-branched polymer layers having high density of primary amine groups on hydroxylated solid supports. Also, this invention relates to a method for growing polymer layers having high density of primary amine group on the solid substrates while utilizing the primary amine on the surface of an aminosilylated substrate to initiate the ring-opening polymerization of aziridine or aziridine derivatives.
2. Description of the Related Art
Silylation, particularly aminosilylation of the surface on solid supports has been applied in a variety of fields including immobilization of biomolecules such as enzyme and antibody, immobilization of inorganic catalysts, modification of electrodes, chromatography, and formation of a self-assembled building foundation using various kinds of molecules such as ionic polymer, nonlinear optical chromophore, fullerene, porphyrin, transition metal complex and inorganic colloidal particle.
The physico-chemical characteristics of the aminosilane layer formed on the surface of solid supports are very important because those determine the structures and the final functionality of the thin film while influencing the shape and the surface density of the immobilized or self assembled molecule.
On the other hand, polymerization initiated on the surface of a substrate has attracted such big attention due to its wide applicability. This invention suggests the fact that new molecular structure accompanying the polymerization can modify the surface properties of a support, and can be chosen to meet various needs. Moreover, chemical bonding between the surface-bound initiator on a support and polymer chain guarantees the excellent stability.
In addition, a xe2x80x9cgrafting fromxe2x80x9d methodology will provide desirable morphologies on the surface of a support. Therefore, it seems natural that people are interested in polymerization initiated on solid supports.
Ulman et al. showed that 2-ethyl-2-oxazoline can be cationically polymerized on a gold surface modified with -hydroxyl thiol (J. Am. Chem. Soc. 120, 243(1998)), and they revealed that surface-initiated anionic polymerization of styrene is advantageous over xe2x80x9cgrafting ontoxe2x80x9d technique (J. Am. Chem. Soc. 121, 1016(1999)). Recently, Grubbs et al. successfully demonstrated that ring-opening metathesis polymerization (ROMP) catalyst polymerizes norbornene at a solid support to make a polymer brush successfully (J. Am. Chem. Soc. 121, 4088(1999)).
It has been generally known that the surface density of the primary amine functional group (xe2x80x94NH2) is about 3.5 amines/100 xc3x852 on the very top surface when a relevant reagent was applied on the surface of a solid support. However, the conventional solid supports having such a low density of primary amine group suffer from limited applicability and therefore need to be improved. A solid support having primary amine groups on its surface is suitable as a substrate for DNA chip or various kinds of biochip. However, the density of 3.5 amines per 100 xc3x852 on the surface of a support is not high enough to hold hydrogels containing DNA oligonucleotides or other biomolecules of different effects because those microbeads need stronger adhesion for the higher reusability. Therefore, the conventional solid supports have not served for the high stability of the biochips and the wide applicability.
The present invention is directed to providing a method for forming molecular layers with high density of primary amine groups on substrates.
The present invention is related to a method for forming molecular layers with high density of primary amine group on solid supports by allowing the primary amine groups on the surface of an aminosilylated substrate to react with aziridine or aziridine derivatives.
This invention is also related to aminosilylated substrates having high density of primary amine groups, generated according to the method of the invention.
The invention is characterized by treating primary amine groups of aminosilylated substrates with aziridine or its derivatives thereby tailoring the chemical and physical properties of the thin films on the substrate. It is preferable to use aziridine of formula 1 
or a protected aziridine derivative of formula 2 